[PATCH] nfs: Fix misuses of folio_shift() and folio_order()

["Matthew Wilcox (Oracle)" <willy@infradead.org>]

Page cache indices are in units of PAGE_SIZE, not in units of
the folio size.  Revert the change in nfs_grow_file(), and
pass the inode to nfs_folio_length() so it can be reimplemented
in terms of folio_mkwrite_check_truncate() which handles this
correctly.

Fixes: 0c493b5cf16e ("NFS: Convert buffered writes to use folios")
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Anna Schumaker <Anna.Schumaker@Netapp.com>
Cc: Christoph Hellwig <hch@infradead.org>
---
 fs/nfs/file.c           |  6 +++---
 fs/nfs/internal.h       | 16 +++++-----------
 fs/nfs/read.c           |  2 +-
 fs/nfs/write.c          |  9 +++++----
 include/linux/pagemap.h |  4 ++--
 5 files changed, 16 insertions(+), 21 deletions(-)

diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index 6bd127e6683d..723d78bbfe3f 100644
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -301,7 +301,7 @@ EXPORT_SYMBOL_GPL(nfs_file_fsync);
 static bool nfs_folio_is_full_write(struct folio *folio, loff_t pos,
 				    unsigned int len)
 {
-	unsigned int pglen = nfs_folio_length(folio);
+	unsigned int pglen = nfs_folio_length(folio, folio->mapping->host);
 	unsigned int offset = offset_in_folio(folio, pos);
 	unsigned int end = offset + len;
 
@@ -386,7 +386,7 @@ static int nfs_write_end(struct file *file, struct address_space *mapping,
 	 */
 	if (!folio_test_uptodate(folio)) {
 		size_t fsize = folio_size(folio);
-		unsigned pglen = nfs_folio_length(folio);
+		unsigned pglen = nfs_folio_length(folio, mapping->host);
 		unsigned end = offset + copied;
 
 		if (pglen == 0) {
@@ -610,7 +610,7 @@ static vm_fault_t nfs_vm_page_mkwrite(struct vm_fault *vmf)
 
 	folio_wait_writeback(folio);
 
-	pagelen = nfs_folio_length(folio);
+	pagelen = nfs_folio_length(folio, inode);
 	if (pagelen == 0)
 		goto out_unlock;
 
diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
index 9f0f4534744b..3b0236e67257 100644
--- a/fs/nfs/internal.h
+++ b/fs/nfs/internal.h
@@ -819,19 +819,13 @@ unsigned int nfs_page_length(struct page *page)
 /*
  * Determine the number of bytes of data the page contains
  */
-static inline size_t nfs_folio_length(struct folio *folio)
+static inline size_t nfs_folio_length(struct folio *folio, struct inode *inode)
 {
-	loff_t i_size = i_size_read(folio_file_mapping(folio)->host);
+	ssize_t ret = folio_mkwrite_check_truncate(folio, inode);
 
-	if (i_size > 0) {
-		pgoff_t index = folio_index(folio) >> folio_order(folio);
-		pgoff_t end_index = (i_size - 1) >> folio_shift(folio);
-		if (index < end_index)
-			return folio_size(folio);
-		if (index == end_index)
-			return offset_in_folio(folio, i_size - 1) + 1;
-	}
-	return 0;
+	if (ret < 0)
+		ret = 0;
+	return ret;
 }
 
 /*
diff --git a/fs/nfs/read.c b/fs/nfs/read.c
index a142287d86f6..ba3bb496f832 100644
--- a/fs/nfs/read.c
+++ b/fs/nfs/read.c
@@ -296,7 +296,7 @@ int nfs_read_add_folio(struct nfs_pageio_descriptor *pgio,
 	unsigned int len, aligned_len;
 	int error;
 
-	len = nfs_folio_length(folio);
+	len = nfs_folio_length(folio, inode);
 	if (len == 0)
 		return nfs_return_empty_folio(folio);
 
diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 2329cbb0e446..7713ce7c5b3a 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -278,8 +278,8 @@ static void nfs_grow_file(struct folio *folio, unsigned int offset,
 
 	spin_lock(&inode->i_lock);
 	i_size = i_size_read(inode);
-	end_index = ((i_size - 1) >> folio_shift(folio)) << folio_order(folio);
-	if (i_size > 0 && folio_index(folio) < end_index)
+	end_index = (i_size - 1) >> PAGE_SHIFT;
+	if (i_size > 0 && folio->index < end_index)
 		goto out;
 	end = folio_file_pos(folio) + (loff_t)offset + (loff_t)count;
 	if (i_size >= end)
@@ -358,7 +358,8 @@ nfs_page_group_search_locked(struct nfs_page *head, unsigned int page_offset)
  */
 static bool nfs_page_group_covers_page(struct nfs_page *req)
 {
-	unsigned int len = nfs_folio_length(nfs_page_to_folio(req));
+	struct folio *folio = nfs_page_to_folio(req);
+	unsigned int len = nfs_folio_length(folio, folio->mapping->host);
 	struct nfs_page *tmp;
 	unsigned int pos = 0;
 
@@ -1356,7 +1357,7 @@ int nfs_update_folio(struct file *file, struct folio *folio,
 	struct nfs_open_context *ctx = nfs_file_open_context(file);
 	struct address_space *mapping = folio_file_mapping(folio);
 	struct inode *inode = mapping->host;
-	unsigned int pagelen = nfs_folio_length(folio);
+	unsigned int pagelen = nfs_folio_length(folio, inode);
 	int		status = 0;
 
 	nfs_inc_stats(inode, NFSIOS_VFSUPDATEPAGE);
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index c6aaceed0de6..df57d7361a9a 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -212,8 +212,8 @@ enum mapping_flags {
 	AS_FOLIO_ORDER_MAX = 21, /* Bits 16-25 are used for FOLIO_ORDER */
 };
 
-#define AS_FOLIO_ORDER_MIN_MASK 0x001f0000
-#define AS_FOLIO_ORDER_MAX_MASK 0x03e00000
+#define AS_FOLIO_ORDER_MIN_MASK (31 << AS_FOLIO_ORDER_MIN)
+#define AS_FOLIO_ORDER_MAX_MASK (31 << AS_FOLIO_ORDER_MAX)
 #define AS_FOLIO_ORDER_MASK (AS_FOLIO_ORDER_MIN_MASK | AS_FOLIO_ORDER_MAX_MASK)
 
 /**
-- 
2.43.0